


ready or knot

by Anonymous



Category: Free!
Genre: Alpha Matsuoka Rin, Alpha Tachibana Makoto, Alpha/Beta/Omega Dynamics, Alternate Universe, Breeding, Explicit Sexual Content, Knotting, M/M, Mating Cycles/In Heat, Multi, Omega Nanase Haruka, Pseudo-Incest, Step-Sibling Incest, Tachibana Makoto Has A Large Cock, Threesome - M/M/M
Language: English
Status: In-Progress
Published: 2020-07-18
Updated: 2020-07-22
Packaged: 2021-03-04 20:01:13
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 2
Words: 4,088
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/25352077
Author URL: https://archiveofourown.org/
Summary: Rin knows that his boyfriend has an eye on his brother. Maybe, he's a bit more into it than he thought.
Relationships: Matsuoka Rin/Nanase Haruka, Matsuoka Rin/Nanase Haruka/Tachibana Makoto, Matsuoka Rin/Tachibana Makoto, Nanase Haruka/Tachibana Makoto
Comments: 6
Kudos: 73
Collections: Anonymous





	1. Chapter 1

It's Friday and that means, Rin's parents aren't home.

It feels like a breath of fresh air to just relax, not under the pressure of being constantly scrutinized and having his head buried in a book. He doesn't know how Haru does it all the time and he doesn't care enough to find out.

On Fridays, Makoto gets to come over after his parents head out on their weekly date and drop the kids off at the babysitter. They watch a movie sometimes, after Makoto finishes cooking dinner for the three of them and they go back to Rin's room, kissing or making out or whatever it is that Rin is in the mood for that day.

It's going a bit differently today.

Rin arches off the bed, shoving his cock deeper down Makoto's throat. He smells the scent pike, Makoto's resulting groan and he slaps a hand over his mouth to keep from moaning out too loud. Haru is home. The last thing he needs is for Haru to be able to tell that they're having sex.

"Mako," Rin whispers, his fingers curling into his bedsheets. His thighs quiver as they lock behind Makoto's neck. "Fuck, that feels so good."

Makoto looks up, a big, innocent smile on his face, saliva smeared around his mouth. It's almost jarring. "Yeah? Are you gonna come?"

"Not yet."

Rin needs more. He's grown especially needy this past week. Maybe it's his rut approaching or maybe it's the fact that he's missed Makoto terribly. Missed his stupid jokes, his food, his mouth, his cock.

"Want your knot." Rin says, simply. Makoto smirks before he swallows Rin down again.

Rin is unable to hold back his moan. His eyes fall shut and he hears a bottle of lube being uncapped. Great, he's about to get fucking railed.

When Rin first met Makoto, there were a number of reasons as to why he was attracted to him. It's not only that Makoto is the nicest person he's ever met or that he's very caring and spoils Rin without being prompted. It's that he has a big dick.

Rin has been with alphas before, some good, some not so much. But, each and every one of them has boasted about their size without actually being well-endowed in that department. Makoto, however. _Jesus _.__

____

____

It still takes Rin four fingers for his boyfriend to fit in there.

Makoto eases a finger into Rin, making the other gasp out and it's not long before another one joins in. He scissors his fingers in a way he knows Rin likes, pouring more lube onto Rin's hole before adding a third. It's sloppy and wet, Rin can hear the loud squelching and he's worried that Haru might hear. The scent neutralizers might not be enough and Haru might find out-

Without any warning, Makoto slides in. He hasn't prepped Rin properly so, Rin can feel the burn of the stretch. "Fuck!" Rin screams and Makoto shushes him with a kiss, which is more tongue and teeth than precision. They kiss sloppily, Rin's hands tangling with Makoto's locks.

Rin backs away, gasping. " _Move _!" He yells and Makoto just smirks, doing as he's asked. He snaps his hips back before pushing all the way in and Rin forgets that he's supposed to be quiet, that his innocent little omega of a stepbrother is home. He unabashedly moans, head hitting the headboard as Makoto thrusts in and out, in and out of him.__

____

____

Rin's eyes roll into the back of his head, drifting into bliss as Makoto pulls out one last time before pushing back in, hitting Rin's prostate perfectly. Rin gasps, a jolt of pleasure passing through his limp body.

The knot is forming, Rin's hole feels like it's being ripped open. It's so good, so familiar. Rin tightens his hand around the head of his cock, fisting it hard enough to make sure he'll pop a knot. It doesn't take long before Rin comes, spurting white all over Makoto's abs. Makoto looks pleased, pressing small kisses to Rin's jaw and the side of his face. Makoto's expression morphs into one of pleasure and Rin feels the first wave of come flooding his insides.

"Ah- ah-" Rin gasps, as he gets filled up, Makoto groaning above him.

"Fuck, I'm gonna breed you so hard, Rin." Makoto says. Even though Rin knows it's next to impossible for an alpha to be bred but, the thought of Makoto fucking him so well that he gets pregnant is enough to get his cock to twitch again.

"Are you gonna carry my kids, Rin?" Makoto teases, his hands wrapping around Rin's ankles and tugging them up. Rin's knees are pushed up to his chest before Makoto pushes in again.

The new angle makes Rin gasp, Makoto's cock directly pushing against his prostate and the speed with which his cock starts to fatten up again in no joke.

"Shit. You really like the thought of that, huh?"

Rin whines, grabbing onto his pillow, his biceps flexing painfully. Every nerve ending of his body feels like it's been set on fire. He's overly sensitive and Makoto is not fucking helping.

Makoto tuts. "My little cockslut." He spits onto his hand to grab at Rin's cock again, jerking him off fast as Makoto fucks him. Rin is going to be too embarrassed to leave the room but, he doesn't care anymore.

Rin comes for a second time before collapsing, pliant and spent underneath Makoto, who's chasing his own climax. One, two, three, Rin counts Makoto's thrusts before he grunts, coming inside Rin's hole again. 

"I'm going to have a marvelous time cleaning this up." Rin complains as Makoto flops down beside him, chest heaving.

"I'll help you, baby. Don't worry about it too much. Just cuddle me." 

"Fucking needy." Rin says, but he falls down on his side next to Makoto, slinging an arm around his boyfriend. "Mm, feels empty, Mako."

Makoto just chuckles, quickly pushing in two fingers and scissoring Rin lazily. Rin sighs, relaxing into Makoto's hold before he eventually drifts off to sleep.

He'll apologize to Haru tomorrow.


	2. Chapter 2

**Summary for the Chapter:**

> can you tell i got carried away with this

Rin finds Haru on the couch, the next morning, with large headphones covering his ears.

Rin flushes deeply in embarrassment, waving to Makoto as he quickly slips out the door. Makoto's eyes linger for a second before he goes, on both Rin and Haru but, he's gone before Rin can ask.

"Mm? Rin?" He mutters and Rin's heart flutters at the way Haru says his name. "G'morning."

"Morning, Haru. Hungry?"

"Yeah, I'll have some-"

"No mackerel." Rin says, watching Haru's eyebrows furrow. "You had that yesterday. And, the day before that. And, the day before that."

Haru frowns, punching Rin in the chest. Rin pretends to get hurt, making a big show of falling onto the carpet and rolling around. Haru just shakes his head, smiling fondly before he gets off the couch and makes his way up to his own bedroom.

It's Rin's job to make them breakfast at least once a week to ensure that Haru gets something other than mackerel in his body. He usually goes for making a simple pancake batter. Especially after last night, Rin barely getting a wink of sleep as Makoto kept waking him up to get him off, he can't even imagine going for making something complicated.

Fuck, right. Last night. He still has to apologize to Haru for disturbing him like that.

Rin winces at the thought. How should he even bring it up? _Hey, Haru. Sorry for making a ruckus, my boyfriend's big cock was up my ass _. Fuck.__

____

____

Rin just pours some batter onto the hot pan, lamenting about how tough his life is when the stairs that lead up to the bedroom, creak.

"The pancakes are on fire." Comes Haru's simple, no-nonsense tone and Rin wants to ask _hey, what did you just say _, when a big red flame bursts up from the pan and nearly burns Rin's eyebrows off.__

____

____

"Shit!" Rin shrieks, throwing the burning pan into the sink. A large waft of smoke comes up and Rin stares, dejectedly, at his meal.

Rin looks back at Haru, who's red in the face and Rin gives him five seconds before he bursts out laughing-

Haru bursts out laughing.

"Shut up, Haru." Rin mutters, unable to keep a smile from appearing on his face as he watches Haru's shoulders shake from how hard he's laughing. _Cute _.__

____

____

"You should've just let me have the mackerel, dummy." Haru says, after he recovers, wiping tears from the corners of his eyes. 

"Fine, whatever you win. Let's have mackerel for the millionth time this year."

Haru beams, an immediate spike in his scent. Rin almost forgets that he's supposed to be angry at Haru for teasing him. "Let's."

So, Rin spends the next few minutes, watching Haru's back as he prepares some fish for the two of them. Rin isn't a pervert or anything (except for when Makoto just somehow manages to bring out that side in him) but, he finds his eyes trailing down, etching into his memory, the curve of Haru's ass.

All familial relations aside, Rin has to admit that his brother is an attractive omega. They'd practically grown up together, Haru presenting just a few months before Rin did and even as a child, Rin often found himself staring at Haru's pink mouth or his back muscles when he swam-

Fuck. The pre-rut phase is really kicking his ass.

This is Haru. His brother. Their parents are married, for fuck's sake.

Yet, Rin's alpha clearly doesn't care. After all, before being Rin's brother, Haru is an omega. A potential mate. Someone who Rin can breed and have pups with.

The tongs that Haru is using to flip the fish, fall from his hand. Haru clicks his tongue and bends over to pick it up. Rin holds his breath.

_Shit, shit, fuck- ___

____

____

Rin's brain just won't shut up. Because, now, his alpha is thinking of bending Haru over and knotting him, till the omega is begging him to stop. He's picturing Haru with a face covered with come, those normally half-moon crescent eyes, widened and shocked.

His alpha wants to breed Haru.

_Shit _.__

____

____

"Rin?" Haru says, tongs clutched tightly in his hand. His expression is unreadable but, Rin knows what he might be thinking.

The smell. The scent of an alpha's pre-rut. It's almost unmistakable.

"Are you okay?" Haru asks, concern mixed in with something else in his eyes.

Rin just wants to jump over the counter and pin Haru to the floor, have the omega ride him till he's shaking. He wants to shove those tongs up Haru's hole, using it as a macabre dildo, just to see Haru filled.

Rin has always seen Haru as an omega before his brother and it's really coming back to bite him in the ass.

"I'm- I'm fine." Rin says. He's not fine. He's getting hard at the fucking kitchen counter. "I'm going to skip breakfast, I think. You can have my share."

"Rin, wait-" 

Rin races up the stairs, locking himself in his bedroom. Fuck, it wasn't supposed to be this bad. The only option he sees is calling up Makoto and asking him to come over.

It's a bad idea, especially because Haru is home and the risk of having his heat triggered earlier than it should be, is an absolute disaster of a thought. But, Rin can't bring himself to care. He just needs to knot something.

With the free hand that isn't fisting his cock, Rin quickly dials Makoto's number. For every passing second that his boyfriend doesn't answer, Rin grows increasingly frustrated.

He's suddenly aware of Haru downstairs, a sizzling pan being held under water and Rin's hand speeds up. Answer, Mako, fucking answer-

"Hey, babe!" Makoto loudly greets. There's some kind of noise in the background, maybe the twins are arguing over who'll marry Haru first. Rin's brain just goes blank. "I got you this shark plush and it looks so much like you, you won't even believe it-"

"Makoto." Rin says, and Makoto immediately shuts up. "How long until you get home?"

"...Rin, you're scaring me. What's wrong?"

"Fuck, that stupid pre-heat-" Rin grunts.

"You're in pre-heat?!" Makoto shrieks and everything on his side of the phone goes quiet. Rin is going to have a great time at the monthly Tachibana dinners after that. His cheeks flush in embarrassment.

"Fuck, Mako! When are you going to be home?!"

"Monday..." Makoto trails off, his voice low. "I'm on that trip, remember?"

"What trip- oh, oh, fuck. Geez. I'm going to die."

Of course, Makoto's trip with his family over the weekend. Just Rin's rotten luck. His boyfriend isn't home the time of his rut.

"Rin. Rin. Did I lose you?"

"No." Rin says, choking on a moan. "But, find a bathroom. Quick."

"Okay, okay. Hang on."

He hears some shuffling on the other side, Makoto whispering something to his mother before he takes off. Rin has his back against the door, fist tightening around the head of his cock to keep himself from coming dry.

Rin has gone through enough ruts to know that unless he knots something- or, someone- there's no way his heat's getting over. And, Rin is not heartless enough to ask Makoto to come all the way back home, just for his rut.

The only thing is, Rin doesn't know what to do anymore.

"Rin? I'm here." Makoto says, concern dripping from his voice. "Talk to me."

"Fuck, Mako. I need you!" Rin screams, despite his inner voice telling him shut the fuck up.

"I know, I know, baby. I'm so sorry." Fuck. Makoto sounds genuinely apologetic. Rin winces as he drops to his knees.

"Don't- don't apologize, it's just the stupid rut talking-"

"I know but, that's not what I'm apologizing for. I must've done something to trigger it- I can't even fucking remember. Shit, Rin, baby. I'm so sorry."

"Jesus, Mako." Rin says, sighing. "Don't make me cry."

"I'm going to fucking die." Rin mutters.

"Rin. Don't kill me."

"Mato, I swear, if you suggest something dumb-"

"Ask Haru." Makoto says, simply. Rin's eyebrows shoot up into his fucking hairline but, the thing he's most aware of, is how his cock twitches in his pants.

"I'm leaving you." Rin replies, moving to hang up the phone, his cheeks aflame.

"Just hear me out!" Mato clicks his tongue. "Haru is an omega, you're an alpha-"

"He's my fucking stepbrother!"

"That didn't stop him from liking you, Rin!"

Rin freezes, his eyes widening. He can't hear Haru anymore outside. Matoko's breathing is labored on the other side

"What?"

"Look, fuck- I wasn't supposed to tell you but, whatever, yeah? Rin, he likes you. I thought it was pretty obvious. I guess not."

Rin holds his breath. "You're joking, right?"

"You think I'd be joking about this?"

"Shit. This is so messed up." Rin mutters. 

"Messed up doesn't even cut it. But right now, you're the priority, Rin. Either you wait for me to come home on Monday and risk extending your rut or..."

"I fuck Haru."

Makoto releases a breath. "Yeah."

There's no way Rin can risk it. His swim meet is on Wednesday. He needs his strength and his focus, none of which he'll have if he's in fucking rut during that time.

He needs this but, Haru... what will Haru say?

"Rin." Makoto says, voice soft. "I want you to be safe, okay? Whatever your decision is, just remember that."

"Sap." Rin mutters but, tears are starting to well up in his eyes.

"Ah, don't cry. You're about to cry." Makoto says and Rin can hear him smiling on the other side. "I don't wanna make my boyfriend cry."

"Too late, dummy." Rin says, sniffling. Makoto giggles and coos at him. They stay like that for a while, just quiet and that's one of the many things Rin loves about them. He never has to fill the silence.

"Hey, so..." Makoto starts. "Have you decided?"

Rin flinches. "I..."

Makoto pauses, waiting for Rin's response.

"I don't think I have an option."

To Rin's surprise, Makoto just hums. He certainly didn't expect Makoto to take this so well.

"You wanna breed him, Rin?" Makoto asks, his voice dropping an octave and Rin gasps in surprise. 

"Th- the fuck?"

"You want him to take your knot? I bet he'd be so good at it."

"Makoto!" Rin shrieks. "Shut up!"

Fuck, fuck, fuck- he feels he's been set on fire. The rut is starting again, flaring up through Rin's poor, exhausted body. All because of Makoto's few words.

"Hasn't Haru always looked like a perfect cockslut to you, hm? Always so willing and eager to help. He won't say no, Rin."

Rin can't understand how Makoto comes up with all this stuff but, it's working. Rin's mind is being pushed into overdrive, just thinking of knotting Haru against the wall outside their parents' bedroom, breeding him to the point where Haru can barely think of anything else.

Rin wants to ruin Haru for anyone else.

He wants Haru to be filled by only his cock.

"Rin?"

"I'll talk to you later, Mako. Love you." Rin says, before he hangs up. He can't think of anything except Haru now.

Haru's room is right across his. 

Rin stumbles out of his room, knocking loudly on Haru's door. He hears a crash on the other side before Haru opens the door, cheeks flushed.

Rin knows Haru can tell. But, Haru still hasn't shut the door in his face.

"Rin..." Haru says, almost cautiously and it's enough for Rin to kiss him.

Haru gasps but, he welcomes it, locking his arms behind Rin's neck and pulling him closer. Someday, Rin will probably regret this moment and his lack of self-control. However, what's now on his mind is just Haru.

Haru and his delightful moans. Haru and his habit of standing on tiptoes while kissing someone. Haru and his legs that are tightly wrapped around Rin's waist now, after Rin made the effort of picking him up.

It feels like ages go by as Rin carries Haru to his bed, breaking away to get on top of him before Rin goes back for another kiss, like a starving man.

Haru's cheeks are flushed, eyes widened as his fingers are fisted in Rin's shirt.

"You triggered my rut." Rin says, plainly. Haru blushes, tugging at Rin's collar hesitantly. Rin moves his attention to Haru's neck, which is looking way too unmarked for his liking.

Haru's back arches further into Rin's tight hold. "How- how did that happen?"

"I don't know." Rin says, nipping at Haru's collarbone to leave a bruise there. "I just really wanted to get you pregnant."

"Oh- oh, fuck." Haru moans. "Are you... are you going to?"

Rin moves down to Haru's chest, teasing a nipple in his mouth while he presses down on the other. Haru shrieks, his hand reaching to grip the back of Rin's neck.

"Am I going to what, Haru?"

"Are you going to breed me?"

Rin stares as Haru averts his eyes, teeth nibbling at his bottom lip.

"I will." Rin says, lowering his mouth to Haru's. "I'm going to."

Rin is painfully hard in his pants and Haru isn't doing much to help it. He needs Haru now. Like right fucking this instant.

Rin moves down to undo Haru's jeans, unsurprised to find the omega's underwear completely soaked. Haru looks positively embarrassed at the sight but, Rin finds it endearing. Just like everything else about Haru.

"Your cock is so small, Haru." Rin taunts, making a show to licking a stripe up the underside of Haru's dick. A wave of slick gushes out Haru's hole, nearly hitting Rin in the face. 

"You're an asshole." Haru pants, fingers in Rin's hair as he sloppily sucks on Haru's cock.

While Haru lies hot and heavy on his tongue, Rin spreads the globes of his ass apart, pushing his thumbs into Haru's pink hole to spread it more. Slick, slick and more slick. It's delightful.

Rin gathers up some of Haru's slick to coat Haru with it, using it to jerk him off. Haru moans, bucking up into Rin's face and Rin speeds up his hand. He just wants to see Haru come.

He's not at the worst part of the rut yet and he wants to make Haru feel good for how much ever little time they've got. He lets Haru know the same.

Haru just nods, eyes glazed over. "Rin, can you... can you make me come?"

"Fuck, of course." Rin just lowers his mouth to Haru's cock, taking him in again. The taste of precome isn't very pleasant but, it's Haru. It's fucking Haru.

Haru thrusts up once, twice before he comes. Rin strokes him through the orgasm, watching Haru's eyes roll into the back of his head. 

"Haru, I'm going to need to-"

Haru doesn't even let Rin complete before pulling his legs up to his chest, presenting his leaking hole to Rin. Rin is unable to hold back his groan at the sight, the thought that he's going to knot his brother ruling him up even more.

Rin is going to show Haru what a real alpha fucks like.

"Gosh, Rin-" Haru pants, his head tipping back as Rin pushes his three fingers in, again.

Rin gets rid of his jeans, giving his cock a few pumps before pushing the head into Haru's hole, circling the rim. Haru moans, his hands clenching the sheets as he thrusts up. He calls out Rin's name, begging him to fuck him and who is Rin to deny his obedient omega?

Rin pushes all the way in, relishing Haru's delightful scream as he bottoms out. He doesn't give Haru a second to adjust as he normally would, just begins to fuck Haru relentlessly. Pistoning his cock in and out of the pliant omega, who takes whatever Rin is giving him.

"Shit, Haru. My perfect little cocksleeve." Rin says, grunting as he fucks Haru within an inch of his life. Haru jostles with every thrust, hands tightening around Rin's biceps and gripping them tightly.

It would be so fucking hilarious if their parents walked in, right now, right this instant to see Rin with his cock deep inside Haru. It would be even more hilarious to see Haru's mother's expression. That bitch made sure to let Rin know that she fucking hated him.

How would she feel to see her dearest, darling son begging for Rin's knot?

Rin looks back down at the omega, his flushed cheeks and bleeding lip. Rin feels the knot form at the base of his cock and he groans, pulling out to push in deeper and Haru jolts, making it obvious that Rin has hit his prostate.

"You're so tight, omega." Rin mutters, slapping Haru's ass once, then twice. "Have you never taken an alpha before?"

"You're too big, you fucking- ah!" Haru screams, Rin's knot is starting to fill him up. The first wave of come hits. "Oh, my fucking God-" 

Even though Rin has had rut partners before, like Makoto and Sousuke but, they're both alphas. Somehow, it's different with an omega. Haru is made for taking a knot, it's how the biology works and Rin has never been more thankful for the fact that his brother is an omega.

While Makoto and Sousuke can't get pregnant, Haru can. Haru can be the father of his children.

"What would your mother say, huh?" Rin asks, as he floods the omega with his come. Haru's eyes widen, his tiny prick twitching. "She'd be so fucking disappointed, you know. Her precious Haru is an an alpha's whore now."

Haru clenches around him, loudly moaning. Rin pulls out, eyes raking over Haru. Haru gasps, loosening his hole and Rin's come spills out. Displeased, Rin gathers it up and pushes it back into Haru.

Having knotted him once, Rin is still not satisfied. Instead, having had a taste of the forbidden fruit, he wants more. Without giving Haru a warning, Rin slips back inside, fucking Haru once more. Haru takes his cock well, like a perfect omega.

It feels like hours go by like this. Rin even picks Haru off the bed and puts him onto the wooden floor. On his knees, with his ass up, Haru has never looked better.

His omega. Haru is his now. There's no way Rin will let go of him.


End file.
